Re, BBC programme: it turns out that the woman who can smell PD is smelling the back, an area of high sebum excretion. Seborrheic dermatitis (SD), a flakey, itchy rash often found on the face or scalp is common amongst PwP.

A research group in Serbia, report [1]:
"a positive correlation between SD, PD and Malassezia presence and density. Our findings that [people with both SD and PD] group had high yeast density and associated high phosphatase and lipase activity in vitro may lead to conclusion that infection is the key mechanism of SD in PD patients. Future better understanding of the interactions between different Malassezia and PD host may provide new opportunities for improved SD control in PD. The appropriate antifungal treatment can be useful for PD patients. Antifungals may reduce Malassezia growth and their enzymes production overall improving patients well-being and quality of life. Correlation between reduction of Malassezia density, positive outcome of SD and the reduction of the non-motile symptoms in PD patients need to be further investigated."

Reference:

[1] "A laboratory-based study on patients with Parkinson’s disease and seborrheic dermatitis: the presence and density of Malassezia yeasts, their different species and enzymes production"
BMC Dermitology, 2014
Valentina S Arsic Arsenijevic,corresponding author1 Danica Milobratovic,2 Aleksandra M Barac,1 Berislav Vekic,3 Jelena Marinkovic,4 and Vladimir S Kostic5
A laboratory-based study on patients with Parkinson’s disease and seborrheic dermatitis: the presence and density of Malassezia yeasts, their different species and enzymes production

John